1. Field of the Invention
This invention relates to a cathode ray tube apparatus wherein a phosphor screen is dividedly scanned by a plurality of electron beams, and a method of manufacturing the cathode ray tube apparatus.
2. Description of the Related Art
In recent years, considerable research has been conducted regarding the development of a standard-format or a wide-screen type high-resolution cathode ray tube suitable for high-quality broadcasting. In general, in order to achieve a cathode ray tube of high resolution, the spot diameter of an electron beam on a phosphor screen must be reduced. To this end, in the prior art, the structure of an electrode of an electron gun assembly was improved, or the caliber and/or length of the electron gun assembly was increased. However, the results obtained so far have not been fully satisfactory, the main reason for this being that the distance between the electron gun assembly and the phosphor screen increases in accordance with an increase in the size of the cathode ray tube, with the result that the magnification of the electron lens increases excessively. Accordingly, in order to achieve high resolution, it is most important that the distance (depth) between the electron gun assembly and the phosphor screen be reduced. In addition, if the deflection angle of an electron beam is increased, the difference in magnification between the center area and peripheral area of the phosphor screen increases. Thus, wide-angle deflection is not advantageous for achieving high resolution.
To overcome the above-described disadvantage, EP 0 471 359 A3 discloses a cathode-ray tube in which a flat face plate is employed and a phosphor screen is continuously formed on the inner surface of the face plate and comprises a plurality of regions which are simultaneously and independently scanned by electron beams emitted from a plurality of electron gun assembles. It is necessary to provided support means in the cathode-ray tube for supporting the face plate against the atmospheric pressure applied thereto.
However, even if the screen is formed integrally and the support means is provided in the cathode-ray tube, a practical problem still remains. Specifically, where scanning is performed simultaneously in plural regions of the screen, it is necessary to employ a simple structure and/or method so as to make connecting portions between adjacent pictures reproduced on the screen invisible.
The above-described cathode ray tube has a plurality of independent electron gun assemblies, and a plurality of deflection units (elemental deflection units, for deflecting plural electron beams emitted from the electron gun assemblies to scan a predetermined number of regions of the phosphor screen dividedly. The number of the deflection units is equal to that of the electron gun assemblies. To hide the connecting portions of adjacent regions scanned independent of one another, it is necessary to adjust the deflection units individually. This can be performed in the case where a small number of deflection units are employed, or where a monochrome image cathode ray tube which can be adjusted in a comparatively simple manner is used. However, an increase in the number of the deflection units will make it difficult to perform such adjustment. Further, in the case of a color image cathode ray tube, it is necessary to perform adjustment for color purity or beam-converging, in addition to such adjustment as moving a reproduced image in the vertical direction and horizontal direction, and/or rotating the same. Thus, it is extremely difficult to adjust all the deflection units appropriately.